1. Field of the Invention
The present invention relates to an image forming apparatus that transfers a toner image formed on an intermediate transfer member to a transfer material.
2. Description of the Related Art
Conventionally, an electrophotographic method using an intermediate transfer method is well known to be used in an image forming apparatus that forms a multiple color image (color image) to a transfer material such as a sheet. With the intermediate transfer method, a plurality of color toners is primarily transferred from an image carrier that carries a toner image to an intermediate transfer member rotated. Thus, a color toner image is formed on the intermediate transfer member. Then, the color toner image formed on the intermediate transfer member is secondarily transferred to the transfer material, thereby forming an image to the transfer material.
On the intermediate transfer member, there is a remaining toner that is not secondarily transferred to the transfer material. A cleaning method is conventionally discussed to remove the remaining toner. As an example of the cleaning method, the remaining toner is charged by a charging member with an opposite polarity of a normal polarity of the toner, and is transferred to the image carrier. In the cleaning, with the increase in number of printed sheets, a part of the remaining toner is adhered to the charging member. Thus, there is an issue of reduction in toner charge performance of the charging member. Japanese Patent Application Laid-Open No. 2004-62085 discusses a method for periodically transferring the remaining toner adhered to the charging member onto the intermediate transfer member.
However, when transferring the remaining toner adhered to the charging member onto the intermediate transfer member, it is necessary to transfer the remaining toner from the intermediate transfer member to a photosensitive drum before the next image formation. If the remaining toner is not sufficiently transferred from the intermediate transfer member to the photosensitive drum, the remaining toner is transferred to the transfer material and may cause an image defect. The charging polarity of the remaining toner is not always uniform. Thus, there is an issue that the remaining toner cannot be effectively transferred from the intermediate transfer member to the photosensitive drum.